The present invention relates to a novel collectin which is useful for investigating mechanisms of biological defense, and is expected to be applied for utilizing as materials for medicines because it may have physiological activities including anti-viral activities and the like.
Collectin is a generic name of proteins having calcium-dependent carbohydrate recognition domain (CRD) and collagen-like region, and the member of these proteins is conceived to involve in basic immunity systems against a wide spectrum of microorganisms such as bacteria and viruses.
The collectins which have been identified heretofore include mannan-binding protein (MBP, SEQ ID NO: 27), surfactant protein A (SP-A, SEQ ID NO: 28), surfactant protein D (SP-D, SEQ ID NO: 29) and conglutinin. These collectins are known to be constituted from basic structures comprising four unique regions of: (1) calcium-dependent carbohydrate recognition domain (CRD), (2) neck region, (3) collagen-like region and (4) N-terminal region containing cysteine [Malhortra et al., Eur.J.Immunol. Vol.22, 1437-1445, 1992] (see, FIG. 1(a)). A subunit can be formed from the three basic structures through making a triple helix in the collagen-like region, and such subunit constitutes an oligomer, e.g., trimer, tetramer and hexamer.
In vertebrates, mechanisms involving cellular immune responses and specific antibody reactions are considered as dominant host-defense systems against inversion of the pathogenic bacteria, viruses and the like. Recently, involvement in nonspecific immune responses of the lectins such as conglutinin has been suggested, for example, it was reported that the lectins may play important roles in neutralizing and removing the various microorganisms in infants having insufficient maternal antibodies and undeveloped specific defense systems [Super et al., Lancet, Vol.2, 1236-1239, 1989].
Moreover, with respect to the roles of the lectins in the biological host-defense systems, it was reported that the host becomes susceptible to infection by, for example, a reduction of the MBP concentration in blood due to genetic mutation of the MBP gene [Sumiya et al., Lancet, Vol.337, 1569-1570, 1991].
The present inventors have found that the conglutinin and the mannan-binding protein can inhibit infection and hemagglutination activity of H1 and H3 Type Influenza A viruses [Wakamiya et al., Glycoconjugate J., Vol.8, 235, 1991; Wakamiya et al., Biochem. Biophys. Res. Comm., Vol.187, 1270-1278, 1992].
Thereafter, the present inventors isolated a cDNA clone encoding the conglutinin, and found that closer correlation may exist between the conglutinin gene and various surfactant protein D gene [Suzuki et al., Biochem. Biophys. Res. Comm., Vol.191, 335-342, 1993].
As described above, the collectin has been expected to be useful in investigating mechanisms of biological defense, and be applicable for utilizing as materials for medicines, however, the presence of any other molecular species belonging to this protein family has not been elucidated.
The present invention was accomplished in consideration of the aforementioned state of art, and is directed to provide a novel collectin which can be expected to exhibit physiological activities such as anti-bacterial, anti-viral activity, especially in human body.
Accordingly, to provide the following polynucleotide and protein which share characteristic structures of those belonging to the collectin family, and which are distinct from the collectins reported heretofore is intended by the present invention:
[1] A polynucleotide comprising the nucleotide sequence which encodes a protein having the amino acid sequence set out in SEQ ID NO: 2;
[2] A polynucleotide comprising the nucleotide sequence set out in SEQ ID NO: 1;
[3] A polynucleotide which encodes a collectin protein wherein said polynucleotide can hybridize under a stringent condition with a probe produced from a genomic clone which shares high homology to a consensus collectin amino acid sequence set out in SEQ ID NO:3 Glu-Lys-Cys-Val-Glu-Met-Tyr-Thr-Asp-Gly-Lys-Trp-Asn-Asp-Arg-Asn-Cys-Leu-Gln-Ser-Arg-Leu-Ala-Ile-Cys-Glu-Phe;
[4] A polynucleotide which can hybridize with any of the polynucleotide according to any of [1] to [3], wherein the protein encoded by said polynucleotide comprises: (1) Ca2+-dependent carbohydrate recognition domain (CRD), (2)neck region. (3) collagen-like region, and (4) N-terminal region containing cysteine;
[5] A collectin protein encoded by the polynucleotide according to any of [3] or [4];
[6] A collectin protein comprising the amino acid sequence set out in SEQ ID NO:2;
[7] A collectin protein comprising the amino acid sequence encoded by the polynucleotide comprising the nucleotide sequence set out in SEQ ID NO: 1;
[8] The collectin protein according to any of [5] to [7], wherein the amino acid sequence of the protein comprises deletion, substitution and/or addition of one or more amino acids, and wherein the protein comprises: (1) Ca2+-dependent carbohydrate recognition domain (CRD), (2)neck region, (3) collagen-like region, and (4) N-terminal region containing cysteine.